In a video processing system, video signals originating from multiple sources (e.g. video cameras, DVDs, VCRs and computer generated images) may be processed and combined into a single aggregate signal, encoded in a particular format, such as NTSC, PAL or High Definition Video. Prior art systems process and combine the different video signals. The systems must provide for generation locking, or “genlock”, to synchronise the video signals and stabilise the image when switching between the video sources or integrating with other equipment. Without a genlock signal for the video signals, an output video signal may lose its continuity when switching between two inputs and phase errors will occur when integrating with other video equipment. To provide a genlock for two video signals, one video signal is selected as a master and a synchronization signal for the other video signal is derived from the synchronization signal of the first signal.
The use of a personal computer (PC) as a video signal processor in professional video processing studios has greatly increased. Commercially available hardware and software products which are integrated into a PC provide a standardized platform for processing the video signals. PCs provide a standardized bus (a PCI interface), an accelerated graphics port (AGP) and a widely-used software platform using Intel-based programming languages.
The digitization of consumer video processing has been facilitated by I/O connections, device drivers and Microsoft software components. Three dimensional (3D) graphics quality and performance levels at consumer price points now rival dedicated graphics systems. Video manipulations in real-time using standard PCs are now of a quality level acceptable for professional television broadcasting. For example, Microsoft Windows Media components provide operating system level routines for MPEG compression and decompression, color space and format conversion of video signals. Recent upgraded versions of the Media components provide increased capabilities over earlier versions.
Several PC-based video processing components are available from companies (such as AJA Video Systems Inc., Leitch Technology Corp., Pinnacle Systems Inc., and Matrox Electronic Systems Ltd.) which provide some capabilities for mixing video signals. However, these components are heavily leveraging hardware-centric designs based on chip-level integration and handle video through dedicated on-board signal paths. Such designs are not fully integrated with three-dimensional hardware of PCs; also they have performance bottlenecks from utilising a single standardised PCI bus. Such designs are not fully scalable to increases in standard 3D capabilities and changes or improvements to WindowsMedia formats or methods. Although these systems provide genlocking of video signals, the genlocking process is set in hardware circuits and, as such, requires a high degree of chip-level integration of such signals with 3D and video processing hardware.
There is a need for a video processing system which can provide real-time processing and genlocking of video signals and 3D graphics in an easily maintainable and upgradeable platform, preferably on a PC-platform, which utilizes available, standardized hardware and software components for improved scalability.